This invention is related to venting and pressure relief systems for use in hydrocarbon storage facilities and more particularly to those systems which stabilize the pressure using the weight of an object.
It is current practice in the petroleum industry to have vent lines running from the underground storage tanks at a service station to an above ground location so that the pressures and vapors in the tanks can be released into the atmosphere. However, environmental regulations will require some restriction on the end of these vent lines to reduce the escape of hydrocarbons into the air.
Several types of pressure/vacuum valves are currently available on the market to perform this function. Most of these devices employ springs to control the relief pressures. However this often proves to be unreliable because the spring forces tend to vary with age, weather conditions, and other factors. Also, the possibility exists for the components to become frozen together because of the moisture trapped therein during subfreezing temperatures. In addition, these type of valves can be fairly complicated to make and therefore quite expensive.